Payment Policies

Policies let you control which chain, scheme, or maximum amount the SDK should use when multiple payment options are available.

Available Policies

Policy	Description
prefer_network(caip2)	Prefer a specific network (e.g. "eip155:8453" for Base)
prefer_scheme(scheme)	Prefer a payment scheme (e.g. "exact")
max_amount(amount)	Reject payments above a threshold (in token decimals)

Usage

from x402_openai import X402OpenAI, prefer_network, prefer_scheme, max_amount
from x402_openai.wallets import EvmWallet, SvmWallet

client = X402OpenAI(
    wallets=[
        EvmWallet(private_key="0x…"),
        SvmWallet(private_key="base58…"),
    ],
    policies=[
        prefer_network("eip155:8453"),  # Prefer Base mainnet
        prefer_scheme("exact"),         # Prefer exact payment scheme
        max_amount(1_000_000),          # Cap at 1 USDC (6 decimals)
    ],
)

How Policies Are Applied

When the server returns multiple payment options, the SDK:

1. Filters out options that exceed max_amount.
2. Sorts remaining options by prefer_network and prefer_scheme scores.
3. Selects the highest-scoring option that has a matching wallet.

If no option matches all policies, the SDK falls back to any compatible option.

Common Network IDs (CAIP-2)

Network	CAIP-2 ID
Ethereum Mainnet	eip155:1
Base Mainnet	eip155:8453
Base Sepolia	eip155:84532
Optimism	eip155:10
Arbitrum One	eip155:42161
Polygon	eip155:137
Solana Mainnet	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
Solana Devnet	solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1